1. Field of the Invention
This invention relates to electrical power distribution and, more particularly, to buses for distributing power in mechanical systems, such as cooling systems for electronic equipment.
2. Description of the Related Art
Facilities with distributed electrical systems often include buses to provide electrical power to various systems in the facility and to electrically connect the systems in the facility with one another and with external systems. A typical bus system in a facility may include many bus bars, bus ways, or similar elongated conductive elements that are attached to one another to form a spine or network. The spine or network may be arranged to provide convenient access points at which to tap into electrical power or make other required electrical connections.
In bus systems that provide electrical power to large components (e.g., mechanical components such as motors), elements of the bus bar system may experience large electrodynamic stresses as the loads from the systems vary during use. For example, when a fan motor operating at 480 volts is switched on, a sudden high amperage may cause electrodynamic stress at a joint between two adjoining bus bars carrying power to the motor. The electrodynamic stresses can cause failures at the junctions between the bus bars. In addition, environmental conditions in some systems may result in additional stresses. For example, a bus system that provides power to mechanical components in an air cooling system may be exposed to thermal cycles in the surrounding air as the cooling system is operated.
Many bus systems use bus bars made of copper to take advantage of copper's high electrical conductivity. Aluminum bus bars tend to be less expensive than copper bus elements for a given current capacity, but aluminum has a higher thermal coefficient of expansion and a lower melting point than copper. These characteristics may make an aluminum bus element more susceptible to mechanical failure when subjected to sudden spikes in amperage through the bus system.